Liquid composition



Patented Feb. 13, 1951 UNITED.

METHOD OF AND LIQUID COMPOSITION FOR LATED ARTICLES CLEANINGELECTBICALLY INSU- Robert T. KBurg, Niagara Falls, N. Y., assign!!- toE. I. du Pont de Nemoursdt Company, Wilmington, Dcl., a corporation ofDelaware No Drawing. Application November 21, 1947, Serial No. 787,471

This invention relates to liquid cleaning com- ;positions andparticularly to liquid compositions %for use in the cold cleaning ofelectrically insulated articles such as electric motor windings and thelike.

There is a large demand for a relatively inexpensive composition of theorganic type for use as a cold cleaner for removing oils, grease, dirtand the like from electrically insulated parts and articles. Gasolenehas been used for that purpose anii eiiects good cleaning, but its useis extremelyhazardous because of its high flammability. Gasolene-carbontetrachloride mixtures have been suggested and used. However, suchmixtures are far from satisfactory due in large measure to the hightoxicity of carbon tetrachloride. Furthermore, even when containing asmuch as 50% by volume of carbon tetrachloride such mixtures have flashpoints as low as about 5 F. and burn at ordinary temperatures so thattheir use involves a serious fire hazard. These and other disadvantagesattending the use of said 6 Claims. (Cl. 134-40) mixtures have beenwidely recognized as being so from the following description of theinvention.

The above objects are accomplished in accordance with the invention bythe preparation and/ or use for the cold cleaning of electricallyinsulated articles and parts, of a solvent mixture containing 36 to 63%by weight of a petroleum naphtha, the remainder of the compositioncomprising methylene chloride and perchloroethylene. I have discoveredthat such mixture are well suited for the use indicated and areoutstandingly superior to solvents or solvent mixtures known and usedheretofore.

The term cold cleaning is used herein to mean cleaning by means of thesolvent mixture in liquid form at a temperature not exceeding about 95F., e. g., at to F. Cleaning at such temperatures is preferablyaccomplished by spraying the article to be cleaned with the liquidmixture. Alternatively, the mixture may be applied to article by meansof a brush or a cloth previously dipped in the liquid. In such methodsthe mechanical action on the dirt particles of, for example, the jets ofspray or the brushing, aidsinthe cleaning. Ifdeslreicleaningmaybeaccomplished by dipping or immersing the article in the liquid. In allsuch instances the cleaning mixture is employed as a liquid, generallyat ordinary temperatures and liquid retained on the article is permittedto evaporate therefrom after the cleaning operation. Evaporation shouldgenerally be carried out in vented spaces or in relatively large wellventilated areas provided for that purpose. The cleaning operation,including drying, usually involves only a minute or so, e. g., up to 2or 5 minutes. Contact of the article with the liquid for more than 5minutes is seldom if ever required, although most commonly usedinsulation materials of the present type may remain in contact with theliquid mixtures for as long as 10 minutes without substantial damage.

The petroleum naphtha constituent of the mixture should have adistillation range within the range 300 to 410 F. and a flash point notlower than F., e. g., 100 to 150 F. as determined by method described inCross Handbook of Petroleum, Asphalt and Natural Gas, published asBulletin No; 25 by the Kansas City Testing Laboratory, pages 650-651 and660. The naphtha should be free of aromatic hydrocarbons such asbenzene, toluene and the like and of unsaturated hydrocarbons. Thewell-known Stoddard Solvent, which is a petroleum naphtha having a.distillation range as indicated above and a flashpoint of not lower than100 F., is particularly well suited for use in practicing the invention.For many uses naphthas having a distillation range within the aboverange and a flash point of 100 to C. is preferred while for certainapplications a petroleum naphtha having a higher flash point, e. g.,around 140 to E, and a distillation range of 350 to 410 C. may bepreferred.

The amount of petroleum naphtha in the solvent mixture should not exceed63% nor be less than'36% by weight. The preferred range is 46 to 57%. Ifsubstantially more than 63% is present the mixtm'e becomes flammable.Mixtures containing less than 36%, i. e., more than 64% by weightmethylene chloride and perchloroethylene, may cause substantial damageto the insulation. The balance of the mixture will comprise methylenechloride and perchloroethylene in a weight ratio of 2 to 5 andpreferably 2.5 to 4.5 parts of the former per 1 part of the latter.

I have discovered that electrical insulation materials which may besuccessfully cold cleaned with the above liquid compositions withoutharm- 3 i'ul effects resulting are those non-thermoplastic resinousmaterial which are adapted for use in' lacquer.

I have found that petroleum naphtha alone is not at all suitable for thepresent purpose in that it is flammable and leaves on the cleaned partsan oily film which facilitates accumulation of dust and dirt thereafter.Methylene chloride or perchloroethylene alone, or mixtures of the two,is also not suitable for use in that substantial damage to electricalinsulation of the types frequently used for motor windings resultstherefrom and in some instances the damage is such as to render theinsulation worthless. The present inven tion is based upon the discoverythat mixtures containing all three of the above ingredients in theproportions indicated accomplish excellent cleaning without leavingobjectionable oily films thereon and without detectable or measurabledamage to the insulation. The fact that such mixtures are relativelynon-toxic and are nonilammable are added important advantages. Thepresent compositions have no flash point up to their boiling points asdetermined by standard open and closed cup methods (described on pages659 and 660 of the above mentioned Handbook of Petrolelnn, Asphalt andNatural Gas), although their vapors will burn with supported combustion.By the latter it is meant that if the vapors 'are added to a flame theywill burn in the flame rather than extinguish it, but they will ceaseburning as soon as the flame is withdrawn.

Generally, it is desirable that compositions for cold cleaning purposeshave a density not substantially greater than that of water andpreferabb lower. The reason for this is that if the density issubstantially greater than that of water the mixture will be pocketedunder water in sumps, pits, and other low places which would beobjectionable for obvious reasons. The present compositions,particularly the preferred compositions, all have densities which aresubstantially equal to or' lower than the density of water and nodifliculty is experienced when using such compositions in their beingpocketed under water as noted above.

The present mixtures are much less toxic than, for example,gasolene-carbon tetrachloride mixtures, and may be used much more widelyand with less danger of harmful physiological efl'ects. As far as isknown, vapors of the present compositions exert no cumulative orpermanent physiological effects upon the human system and in thisrespect as vastly superior to mixtures containing carbon tetrachloride.However, as is the case with all organic vapors and gases, undueexposure of workers to vapors from the mixtures should be avoided andbest practice involves using the mixtures in well ventilated areas.

Specific examples of the present cold cleaning compositions are shown inthe following examples in which concentrations of the components areexpressed in weight percent.

Example 1 Percent Petroleum naptha, distillation range 302 to 392 F.,flash point F 57.0 Methylene chloride 34.5 Perchloroethylene 8.5

The above composition was used to remove oily and greasy dirt from a 350 H. P. 2200 volt synchronous motor winding at room temperature by thespraying method. The cleaning action was,

rapid and eflicient and no obnoxious odor was noted by the workmen. Thecomposition had a density of and, hence, did not pocket under water inlow places. Solvent which adhered to the motor winding evaporatedrapidly after the spraying to leave the part in a dry clean conditionwithin a total elapsed time of about 3 minutes. No visible damageto thealkyd resin type insulation could be detected and dielectric strengthtests showed no loss whatsoever in its insulating value.

Example 2 Percent Petroleum naphtha, distillation range 302 to to 392F., flash point 105 F 46,0 Methylene chloride 38.5 Perchloroethylene15.5

Example 3 Percent Petroleum naphtha, distillation range 350 to 410 F.,flash point F 57.0 Methylene chloride 34.5 Perchloroethylene 8.5

Example 4 Percent Petroleum naphtha, distillation range 350 to to 410F., flash point 145 F 46.0 Methylene chloride 38.5 Perchloroethylene15.5

Compositions 2, 3 and 4 may be used as described in Example 1 to givesubstantially the same results. Parts insulated with any of thenon-thermoplastic resinous materials specifically set forth hereinabovemay be successfully cleaned in a similar manner.

In addition to being relatively non-toxic and non-flammable as comparedwith gasolene-carbon tetrachloride compositions used heretofore forsimilar purposes, the present compositions have the further distinctadvantage of being noncorrosive. Carbon tetrachloride and compositionscontaining the same are notoriously corrosive to various industrialmetals, particularly in the presence of moisture, in view of whichcorrosion of containers and of delicate electric parts by carbontetrachloride mixtures has been recognized as a serious disadvantageattending their use. In contrast, no corrosion problems are presented ineither the storage or use of the present compositions even under moistconditions.

I claim:

1. A liquid cleaning composition for the cold cleaning of solidelectrically insulated articles and parts to remove therefrom oils,greases and dirt, comprising 36 to 63% by weight of a petroleum naphthahaving a .distillation range of 300 to 410 F. and a flash point notlower than 100 F., the remainder of the composition comprising methylenechloride and perchloroethylene in a weight ratio of 2 to 5 parts of theformer to 1 part of the latter.

2. A composition according to claim 1 wherein the weight ratio ofmethylene chloride to perchloroethylene is 2.5 to 4.5 parts of theformer to 1 part of the latter.

3. A composition according to claim 1 wherein the naphtha content is 46to 57% by weight.

4. The composition according to claim 3 wherein the weight ratio ofmethylene chloride to perchloroethylene is 2.5 to 4.5 parts to 1 part ofthe latter.

- 5. A method of removing oils, greases and dirt from solid electricallyinsulated articles, comprising subjecting such articles at a temperaturenot greater than 95 F. to the action of a liquid composition comprising36 to 63% bv weight of a petroleum naphtha having a distillation rangeof 300 to 410 F. and a flash point not lower than 100 F., the remainderof said composition comprising methylene chloride and perchloroethylenein a weight ratio of 2 to 5 parts of the former to 1 part of the latter,and limiting contact of said e 6 articles with said liquid compositionto not more than 10 minutes duration.

6. A method of removing oils, greases and dirt from electricallyinsulated articles, comprising subjecting said articles at a temperaturenot greater than F. to the action of a liquid composition comprising 46to 57% by weight of a petroleum naphtha having a distillation range of300 to 410 F. and a flash point not lower than F., the remainder of saidcomposition comprising methylene chloride and perchloroethylene in aweight ratio of 2.5 to 4.5 parts of the former to 1 part of the latter,and limiting contact of said articles with said liquid composition tonot more than 5 minutes duration.

ROBERT T. KBURG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

1. A LIQUID CLEANING COMPOSITION FOR THE COLD CLEANING OF SOLIDELECTRICALLY INSULATED ARTICLES AND PARTS TO REMOVE THEREFROM OILS,GREASES AND DIRT, COMPRISING 36 TO 63% BY WEIGHT OF A PETROLEUM NAPHTHAHAVING A DISTILLATION RANGE OF 300 TO 410* F. AND A FLASH POINT NOTLOWER THAN 100* F., THE REMAINDER OF THE COMPOSITION COMPRISINGMETHYLENE CHLORIDE AND PERCHLOROETHYLENE IN A WEIGHT RATIO OF 2 TO 5PARTS OF THE FORMER TO 1 PART OF THE LATTER.
 5. A METHOD OF REMOVINGOILS, GREASES AND DIRT FROM SOLID ELECTRICALLY INSULATED ARTICLES,COMPRISING SUBJECTING SUCH ARTICLES AT A TEMPERATURE NOT GREATER THAN95* F. TO THE ACTION OF A LIQUID COMPOSITION COMPRISING 36 TO 63% BYWEIGHT OF A PETROLEUM NAPHTHA HAVING A DISTILLATION RANGE OF 300 TO 410*F. AND A FLASH POINT NOT LOWER THAN 100* F., THE REMAINDER OF SAIDCOMPOSITION COMPRISING METHYLENE CHLORIDE AND PERCHLOROETHYLENE IN AWEIGHT RATIO OF 2 TO 5 PARTS OF THE FORMER TO 1 PART OF THE LATTER, ANDLIMITING CONTACT OF SAID ARTICLES WITH SAID LIQUID COMPOSITION TO NOTMORE THAN 10 MINUTES'' DURATION.